1. Field of the Invention
The present invention relates to a method and apparatus for image forming, and more particularly to a method and apparatus for image forming capable of effectively collecting waste toner generated in a toner image forming process.
2. Discussion of Background Art
In a background image forming apparatus, a toner image is formed on a surface of a photoconductor according to an electrographic method, and the toner image is transferred to a recording medium. In another background image forming apparatus (i.e., color image forming apparatus), toner images of different colors are formed on surfaces of a plurality of photoconductors according to the electrographic method. The toner images are sequentially transferred first to an intermediate transfer belt and then to a recording medium.
In these types of image forming apparatuses, toner remains on the surface of the photoconductor or the intermediate transfer belt after a toner image is transferred from the photoconductor or the intermediate transfer belt to the recording medium. The toner remaining on the surface of the photoconductor or the intermediate transfer belt is collected as waste toner by a cleaning device. The collected waste toner is stored in a waste toner collecting unit. When the waste toner collecting unit is filled or nearly filled with the waste toner, the waste toner collecting unit is detached from an image forming apparatus to be replaced by a new, unfilled waste toner collecting unit. Whether the waste toner collecting unit is filled or nearly filled with the waste toner is detected by a sensor.
In one of the background image forming apparatuses described above, a box-shaped, transparent toner storing container is provided on a bottom of the waste toner collecting unit. The toner storing container is set to a position between a light emitting part and a light acceptance part of an optical penetration sensor, when the waste toner collecting unit is attached to the image forming apparatus. The waste toner collecting unit includes a tube having an opening at an upper end in an upper area of the toner storing container. Thus configured, when the waste toner collecting unit is actually filled or nearly filled with the waste toner, the waste toner starts flowing out of the toner storing container from the opening at the upper end of the tube. As a result, light emitted from the light emitting part and received at the light acceptance part is intercepted. This interception of the light indicates that the waste toner collecting unit is filled or nearly filled with waste toner.
In this system, however, the waste toner may be stirred up due to impact caused when the waste toner is put in the waste toner collecting unit or due to rotation of a conveying member which conveys and levels the waste toner. Then, a part of the waste toner enters in the toner storing container from the opening at the upper end of the tube. As a result, the light emitted from the light emitting part is intercepted before the waste toner collecting unit is actually filled with the waste toner, and it may be incorrectly detected that the waste toner collecting unit has been filled or nearly filled with the waste toner.
Further, if one of waste toners of a plurality of colors (e.g., waste toner of the magenta color) put in the vicinity of the tube is relatively large in amount, this waste toner may accumulate more in the vicinity of the tube than in other parts of the waste toner collecting unit. As a result, this waste toner enters into the toner storing container through the tube and intercepts the light emitted from the light emitting part before the waste toner collecting unit is actually filled with the waste toner. Thus, a premature detection that the waste toner collecting unit is filled or nearly filled with the waste toner may result.
This incorrect detection leads to replacement of a waste toner collecting unit with a new waste toner collecting unit before the waste toner collecting unit is actually filled with waste toner. As a result, the replacement of waste toner collecting units takes place more often than necessary, thus increasing the cost of replacements. Further, the replacement of the waste toner collecting units interrupts use of the image forming apparatus. Therefore, operating efficiency of the image forming operation is reduced.
In this background image forming apparatus, the waste toner placed in the waste toner collecting unit is horizontally conveyed exclusively by a single conveying member. The single conveying member, however, has limited waste toner conveying power. Therefore, if a series of images of a relatively large image area are formed, and a relatively large amount of waste toner is successively put in the waste toner collecting unit, the waste toner is accumulated in a pile and stops more waste toner from entering the waste toner collecting unit.